Device and method for measuring deformation of a mechanical test specimen

A device for measuring the deformation of a mechanical test specimen, and including a pressing member (3) for stressing a substantially flat specimen (16) in controlled manner by means of a punch (25); a Michelson interferometer having an optical branch (9d) defined optically by a first face (16b) of the specimen (16), and for generating interference images related to the deformation of the specimen (16); a telecamera (44) for acquiring and digitizing the interference images; and a processor (27) for processing the digitized images and controlling the measuring process fully automatically. The interferometer (9) may alternatively perform white light interferometry measurements, ESPI measurements, or ESPI profilometry measurements, by simply substituting the light source and control software.